Divide by Three


I’m pretty sure you know what the four basic operations in mathematics are. They are addition, subtraction, multiplication and division. This article is about division. More specifically, this article is about how to divide by three.

Are you really good at mathematics?

How many of you are good at basic mental mathematics? How many of you can divide by three using your head? It’s easy right? We’ve been doing this since we were kids! But how many of you desperately need a calculator even for a simple calculation? Flashback to a meme about needing a calculator to verify that 8+5 is 13! I’m pretty sure most of you would prefer to have a calculator at your exams even if it is to divide by three.

Do you remember that booklet with logarithmic tables? Remember the days when we poured over these tables just to do one question in our ordinary level mathematics paper? If you did physical science or biological science for your advanced level examination, I’m sure you spent many nights engrossed in this book doing your past-papers. But just out of curiosity, has anyone of you ever used a log-book to divide by three? Only me? Really?

using a log book to divide by three

I remember that day quite well! It was our first physics practical of our A-level class. Our instructor said, “Today we take measurements from a Vernier Caliper. Take 3 readings of every object and get the average. If there are any difficult calculations, use your log books!” And that’s exactly what I did. 5 minutes later, I got a punch from my best friend. I turned around to see him bursting with laughter. “Why?” I asked him. “Nothing!” was the reply. “You sure everything’s alright with you?” “You idiot! You’re using a log table to divide by three!”

What can this story teach me?

Reflecting on this incident almost 5 years later, I came across an interesting parallel scenario. We encounter so many problems in our everyday lives. Yet most of those problems aren’t limited to a single solution. Let me rephrase that. There are many different ways to solve the same problem. I could’ve used my head, my calculator, or even my log book to divide a number by three; and each time, I’d get the same answer. However, there maybe even more methods that I never explored, like doing long division on a piece of paper.

But even though these methods converge at the same solution, each method has its own pros and cons. Some methods are fast and cost effective, but only work under certain conditions. Some methods are tedious, but they are very cost effective and work under almost all conditions. There are also methods which are very fast, works under all conditions, but not very cost effective. It’s up to us to find the best method according to our situation.

Who knows? You might find a better way to divide by three!

Note: This article was adapted from my speech titled “Divide by Three” delivered at Kristo, University of Kelaniya, as my 4th project in the Competent Communication Series.

Image Credits: Ishani Senadhipathi, Gavel Club – University of Colombo

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